1. Field of the Invention
The present invention relates to a method of fault diagnosis in a system having a plurality of sensors and a plurality of functional parts which directly or indirectly relate to the sensors.
2. Description of the Related Art
In a complex system comprising a plurality of devices, electronic controlling of various devices has been developed along with the rapid advance of electronics. The advantage has been brought in improving reliability of the system by adopting the electronic controls, while there is the drawback that the electronic parts become a black box when there is something wrong with the system resulting in difficulty of locating failures.
To cope with this drawback, it has been disclosed that a fault diagnosis function is incorporated into a control system of vehicle by Japanese Kokai No. SHO 61-107436. In the prior art, predetermined fault diagnosis signals are outputted to each part from a control unit which controls the system, and it is judged to be faulty when a predetermined response signal corresponding to the fault diagnosis signals cannot be obtained.
In addition to such electronic controllers and sensors, such system has many actuator parts. In an automobile, for example, the parts are a stepping motor for driving a throttle, various solenoids for driving various members, and so on. These parts, sensors, actuators and electric wires which connect the sensors and actuators comprise a set of "functional parts".
Such functional part set can easily become a "black box", because these parts are mutually related.
For example, from the functional point of view, an engine comprises an engine body, air-intake subsystem, fuel supplying subsystem, ignition subsystem, exhaustion subsystem, which are mutually associated. If there is something wrong with the air-intake subsystem, the failure in the air-intake subsystem effects the main body of the engine and generates knocking or it further effects the exhaustion system resulting in increase of the temperature of the exhaustion gas. Therefore, even if abnormality in the exhaustion temperature is detected, it cannot be always concluded that the failure is occurring in the exhaustion system.
To cope with this problem, it has been studied that sensor information is patternized as fault diagnosis data based on the knowledge, attained by the experiences of mechanic engineers, and stored in a control unit in advance, and then, a pattern matching method is applied. However, failures which have never been experienced cannot be coped with by the conventional method, thus limiting applications of the diagnosis.